Milo g



Patented Oet.26,1897.

M. e. KELLoee. MULTIPLE SWITGHBOARD.

(No Model.)

y No. 592,412.

FFICE MIL() G. KELIOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SIVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M ULTIPLE SWITCHBOARD.

SPECIFICATION forming' part of Letters Patent N0. 592,412, dated October 26, 1897. Application tiled September 8, 1891. Serial No. 405,094. (No model.)

To @ZZ whom, t may concern.-

Bc it known that I, MILO Gr. KELLOGG, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing', forming a part of this specication.

My invention relates especially to a groundcircuit telephone-exchange system in which induction-coil translators or converters, one for each line at the central office, are employed to translate the telephone-currents from one circuit or line to another circuit or line.

It consists of a system for calling, switching, testing, and clearing-out signals for such an exchange which I shall describe and claim in detail.

The accompanying drawing, illustrating my invention, represents sectional views of two switchboards with the central-office switches and apparatus for two lines of the exchange and the connecting and answering apparatus at each board for answering calls, connecting the translators of the two lines, testing to see whether the lines are in use,` and receiving clearing-out signals for a connection which may be made. l

A A' are two switchboards. Other boards may be added and used as required for the size of the exchange. Each board has a metal socket or switch contact-piece for each line.4 These sockets or contact-pieces are marked 'j j and are each adapted to receive the switchplugs at the board and thereby form contact with the contact-piece of the plug and also to have the plug contact-pieces applied to them for testing, as will hereinafter be described.

I I are two ind notion-coil translators or converters, one for each line, with relay-armatures and attachments such as will be described.

w w are two annunciators, one for each line.

At each board there is a pair of plugs, (marked D D,) a test-battery for the pair of plu gs,(marked B,) a clearing-out annunciator for the pair of plugs, (marked 12,) two callingkeys for the pair of plugs, (marked 7c 7c,) an

operators telephone, (marked 15,) a looping-in switch for the pair of plugs, (marked Y,) and a calling-generator, (marked B.)

The switch Y has two levers and two pairs of contact-bolts on which the levers may alternately be placed.

The plugs are adapted to be inserted into the switch-holes of the terminals jj at their board and forni connection with the terminals. The keys 7c la have each a lever normally in contact with a point and another point against which the lever comes into con tact when it is pressed away from the firstmentioned point.

One of the plugs is connected by a iiexiblc conductor to one of the key-levers, and the other plug is similarly connected to the other key-lever.

Thetwo points against which the levers normally press are connected to the two lcvers of the switch of the pair of plugs.

The bolts of one pair of the contact-bolts with which the levers of the switch Y may be placed in contact are connected together through the operators telephone, and the other pair are connected together through the clearing-out annunciator of the pair of plugs.

.The test-battery of the pair of plugs is connected in circuit with one of the cords.

The contact-piece connected to plug D of the plugs'D D extends, as shown, to the bottom of the handle and rests normally on the metal strip c.

The induction-coil translators I I have each an armature placed so as to be attracted and moved by the core of the translator when a battery-current of suitable character passes through one of its coilsA and a contact-point against which the armature normally closes and from which it is separated when the armature is thus moved and another contactpoint from which the armature is normally separated and with which it is closed when the armature is moved.

Each of the ground-circuit lines passes through one coil of its translator and thence to the armature. The first-mentioned contact-point of the translator of the line is grounded through the line-annunciator, and the other contact-point of the translator is grounded, but not through the annunciator.

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One side of the other coil of the translator of the line is connected to all the metal sockets jj of the line, and the other side of said coil is connected by a Wire or metallic-circuit connection with the same side of all the other coils of the exchange whichv are connected to metal sockets jj. As the circuits of these coils are local to the exchange, they may be called the local coils of the translators.

One side of the generator is connected to each of the lower of the normally open contacts of the calling-keys 7c lo, and the other side of the generator is connected by metallic connection with said metalliccircuit connection mentioned above. The metal plates o, with which the contact-pieces of the plugs D D normally connect, are also metallically connected with said metallic-circuit connection.

The subscribers-station apparatus may be of the usual form used for ground-circuit lines.

The operationof the system is as follows: When a subscriber desires a connection, he operates his generator While his telephone is on the switch. A signal-current passes from his ground connection through the line to ground at the central oflice, through the norinally closed pair of contact-points of the translator and the line-annunciator, and operates the annunciator. When the operator to whom the annunciator is assigned observes the indication, she places one of her plugs D in the metal socketj of the line, and the levers of the switch Y being in position, so that her telephoneis in circuit with the plug, her telephone is in a closed circuit with the local coil of the translator of the line and the battery B which belongs to the plug. This circuit is, say, from the metal socketj through the local coil of the translator to said metalliccircuit connection of the exchange to the mate D' of the plug, through its contact with plate o, and thence through the operators telephone and the test-battery B to the plug D, which is inserted in the metal socket. The operator then by conversation finds out what line is Wanted, and she tests the line,

as will hereinafter be indicated, and if she finds it to test free or not in use she places the plug D of the pair of plugs in the metal socket of that line. The local coils of the translators of the tWo lines are thereby included in a closed metallic circuit which is local to the central office and contains the` test-battery B. The operator then presses on the key 7c, which is connected to the plug D', and the calling-generator is included in a local circuit with the local coil of the translator of the line Wanted, and an induced current will be generated in that line and will ring its signal-'receiving bell at the subscribers station. The operator then moves the lever of the switch Y so that the clearingout annunciator is in circuit with the pair of plugs.

The test-batteries B B should be of such strength that when one of them is included, as above described, in a closed circuit with a local translator-coil, it willcause the armature of the translator to be attracted, so as to open its pair of normally closed contacts and close the pair of normally open contacts. The ground connection of the line at the central office through the annunciator is thereby opened as soon as connection is made with one of its metal sockets j j, and the line is grounded, but not through the annunciator, by the closing of the armature with the normally open contact.

The batteries and clearing-out annunciators should be so related as that the annunciators will not be operated by the batteries when'connected as described. For this purpose they may be made less sensitive than the relay part of the line-translator.

To send a clearing-out signal, either subscriber operates his generator and a current passes over his circuit and an induced current is thereby generated in the circuit which contains his local coil and operates the clearing-out annunciator which is in circuit with the local coil. The test-battery which is also in circuit will reinforce the clearing-out current generated by the subscriber, so as to insure that the clearing-out signal shall be indicated when either subscriber sends a clearing-out current over his line, which is translated at the central oflice into the circuit which contains the clearing-out annunciator. The use of the battery to thus reinforce the clearing-out-signal current is of importance in that it allows of the use of such forms of translators as are best adapted to telephonecurrents and without special consideration of their being best adapted to translate signaling-currents and of causing the clearing-out annunciator to be operated in the secondary circuit. v

Itis well known that translators of the constructions which are best adapted to translate the feeble rapidly-alternatin g currents of telephonic transmission are not those best adapted to translate the stronger and less rapidly alternating currents generated by the subscribers generators-that is, a form of Vtranslator which best translates the telephone-currents into the secondary circuit will produce in the same circuit an unduly Weak secondary c urrent from the subscribers calling-generator for clearing-out purposes, and thus would make the operation of the clearing-out annunciator uncertain and unreliable were the most suitable translators used for telephone-currents. as described to reinforce the clearing-out cu rrent reliability in the clearing-out operation would only be obtained by the use of such constructions of translators as would not give the best results for the telephone-currents".

By my organization, however, with .the battery employed, as described, to reinforce the clearing-out current such forms of translators may be employed as are best adapted to translate the feeble rapidly-alternating currents of telephony, and at the same time reliability in With the:use of the battery.

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the operation of the clearing-out signals may be obtained.

As the ground connection of the line through the line-annunciator is open when the clearing-out signal is sent, the subscriber sends the signal without operating the lineannunciator.

The test system is as follows: Each operator has a test-plug T and an induction-coil t'. One coil of the induction-coil is in circuit with his telephone. The test-plugis connected to a flexible conductor, by which it may be carried into contact with any metal socket j atits board and is connected through the other coil of the induction-coil with the heretoforementioned metallic-circuit connection of the exchange.

NVhen the operator tests a line, she places her test-plug on its metal socket. If the line is not in use, no complete circuit is established which contains a battery and one coil of the induction-coil, and her telephone will not respond. of the line has a switch-plug in it, as above described, a complete circuit is established which includes the coil and a battery, and the telephone will respond, indicating that the line is in use. This circuit may be traced thus: from the test-plug to the metal socket in which is a switch-plug, thence to the mate of the plug through the battery B', thence to the metallic circuit of the exchange, and thence through the coil of the induction-coil Ai to the test-plug.

It will be observed that in this system the ground connection of each line through its annunciator is opened when the line is switched for conversation, and the line is grounded through a circuit connection which does not include the annunciator; also, that the line has the translator-coil in circuit with it whether it is grounded through the annunciator or not. From this organization it results that an operator sends a calling-signal to any line without operating the lineannunciator, and any subscriber sends the clearing-out signal without operating his lineannunciator, whereas if the annunciator remained in circuit during conversation it would produce a retardation eifect on the telephone-currents, and when signals were sent by the operator on making connection or clearing-out signals sent by the subscriber after completing' a conversation the linean nunciator would also indicate a call, and since in multiple-switchboard systems the annunciator of a line is frequently at another board than that where the connection is made great confusion would occur in the operation of the exchange.

Other ways than that described may be employed to remove the annunciator from the line-circuit when the line is switched for conver`saton--as, for instance, the annunciator may be shunted or short-circuited by suitable relay-contacts when the line is switched If, however, any metal socket i and thereby practically removed from the circuit.

I claim as my inventionl. Inatelephone-exchangesystem,aswitchboard, telephone-lines, each permanently grounded at the outer end and normally Y grounded at the central office through its annunciator, and translators at the central office for said lines, one for each line, one coil of which is in the circuit of the line, in combination with a normally open ground connection for each line which does not include the line-annunciator, a connect-ion between one side of the other coil of the linetranslator and the same side of the same coil of each of the other translators, and switch apparatus to connect the other side of said coil of the line-translator with the same side of the same coil of any other translator and close said normally open ground connection of the line as long as its translator-coil is thus connected.

2. In a telephone-exchange system, telephone-lines, each permanently grounded at its outer en d, a ground connection with which it is normally closed, a line-annunciator in such ground connection, and translators at the central office, one for each line, one coil of which is in the circuit of the line, in combination with a second ground connect-ion for each line which does not include the line-annunciator and is normally open to the line, a connection between one side of the other coil of the line-translator and the same side of the same coil of each of the other translators, and switch apparatus to connect the other side of said coil of the line-translator with the same side of the same coil of any other translator and as long as the translator is thus connected open the iirst-mentioned and close the secondmentioned ground connection of the line.

3. In a telephone exchange system, two telephone-lines, each permanently grounded at their outer ends and grounded at the central oiiice while and as long as switched for conversation between subscribers,and trans lators at the central oilice for said lines, one translator for each line, one coil of which is in the circuit of the line between such grounds of the line, the other coils of the translators being connected into a complete circuit for conversation, in combination with a clearingout annunciator and a battery in said complete circuit of the two coils, and calling apparatus at each subscribers station to send a clearing-out current through his line, said battery being made of too little strength to cause the clearing-out annunciator to be operated when they are in said complete circuit of the two coils but reinforcing the clearingout current sent by either subscriber to insure the operation of the annunciator.

4. In a telephone exchange system, two telephone-lines, each permanently grounded at its outer end and grounded at the central oflice while and as lon g a's switched for conver- IOO IIO

sation between subscribers, and translators at the central office for said lines, one for each line, one coil of which is in the circuit of the of said last-mentioned coils, and calling apparatus at each subscribers station to send a clearing-out current through his line, said 1 battery being made of too little strength to cause the clearing-out annunciator to be op' l one for each line,r one coil of which is in theL circuit of its line, the other coils of the linetranslators being temporarily connected together into a complete circuit for conversation, and said lines being grounded at the central office while, and as long as switched for conversation between subscribers, their coils are thus connected by circuit connections which do not include the line-annunciators, in combination with a clearing-out annunciator in said complete circuit of the two coils, and calling apparatus at eachsubscribers station to send a calling-current through his line.

6. In a telephone-exchange system, telephone-lines, each permanently grounded at its outer end, and. translators at the central office for said lines, one for each line, one coil of which is in the circuit of the line, each translator having two pairs of contacts operated by an armature, one pair being normally closed and the other pair normally open, one contact of each pair being connected with the line, the other contact of the normally closed pair being grounded throughthe lineannunciator, and the other ,contact of the normally open pair being grounded but not through the line-annunciator, in combination with switching apparatus to connect together into a circuit any two of the other coils of the translators for conversation between subscribers, and a battery in any circuit thus established, said battery as long as two coils are thus connected acting on the translatorcores through the coils with which it is in circuit to move the armature of each of the two translators to openthe normally closed and close the normally open pairs of contacts.

l7.'In a telephone-exchange system, telephone-lines each permanently grounded at its outer end, and translators at the central ottice for said lines, one translator for each line, one coil of which is in the circuit of the line, each translator'having a normally open pair of contacts operated by an armature of the translator, one Contact being connected to the line and the other to the ground, in

i combination with switching apparatus to conynect together into a circuit any two of the other coils of the translators, and battery in circuit with each coil as long as thus connected, said battery acting on the translatorcoils with which it is in circuit to move the armature of cachot' the two translators to y close its said pair of contacts.

8. In a telephone-exchange system, two

`telephone-lines permanently grounded at their outer ends and each normally grounded at the central oflice through its line-annunciator, and translators at the central office for said lines, one for each line, one coil of which is in the circuit of the line, the other i two coils being temporarily connected into a circuit for conversation between the two subscribers, and thetwo lines being then or as long as the coils are thus connected grounded at the central oftice and not through the lineannunciators.

9. In a telephone-exchange system, subscribers telephone lines, callin g-annuncia- 1 cuit with its line, switches on a switchboard,

l having each a contact-piece, electromagnetic tors, one for each line, each normally in a cirone for each subscribers talking-circuit and 1 devices other than said line-annunciators, 1 one for each line, each operated when a current is established through it, and thereby con- 1 trolling the line-annunciator that it will not then be operated and made to indicate a ca-ll by a current sent over the line, pairs of switchi plugs, each plug having a contact-.piece adapted to form connection with said contact-piece of the switch of a subscribers.talking-circuit :when the plug is placed in said switch to :switch said talking-circuit for conversation, t said contact-pieces of the pair of plugs being I connected together by a flexible switch-conductor, said contact-piece of a line being connected to one side of its electromagnetic devtors so that they shall not then be operated by currents sent over the lines from either subscribers station.

l0. In a telephone-exchange system, multiple switchboards, subscribers telephonelines, annunciators, one for each line, each normally in a circuit with its line, switches, one on each board for the talking-circuit of each subscriber and having each a contacti piece, electromagnetic devices, one for each line, each actuated when a current is established through it to so control the line-annunv ciator that it will not then be operated by, a

current sent over the line, pairs of switchplugs at each board, each plug having a contact-piece adapted to form connection at its IOO board with said eontaepieees of the switches of the subscribers talkingirenits when the plug is placed in either of said switches to switch t talking-circuit for conversation, said contact-pieces of ezteh pair of plugs being eonneoted together by zt flexible switch-conductor, said contact-pieces of a line being connected to one side of its electromagnetic device, and the other sides of the electromagnetie devices being connected together, and 1o a battery in the eireuit between said contactpieces of each pair of plugs.

In testimony whereof I have hereunto subscribed my neme.

` MILO G. KELLCGG. Witnesses:

CALVIN Dn WOLF, R. B. BELL. 

